Shock Compensation Who are we? Team members: Max Madore Joseph - - PowerPoint PPT Presentation

VCSO Mechanical Shock Compensation

Who are we?

Team members: Max Madore Joseph Hiltz-Maher Shaun Hew Shalin Shah Advisor: Helena Silva Phonon contact: Scott Kraft

• VCSO and mechanical vibration
• Analog filter for compensation of 20dB
• Expand compensation to three axes

Project Overview

Original Goals

• Measure Instantaneous Frequency shifts and

compare with accelerometer voltage output

• Design Compensation circuit based on

frequency/voltage characteristics

• Test in and implement in 3 axis to determine the

unique responses of each

Previous Work

Last Year:

• Creation of Shock Tower for repeatable tests
• Comparison of two identical VCSOs
• Measurement Using Oscilloscope

Problems:

• Unreliable Data
• Mismatched VCSO frequencies

VCSO

• Nominal frequency of

400MHz

• Embedded Quartz crystal

with varactor

• Voltage controlled with

linear sensitivity between roughly 1V and 3V

Frequency Matching

Frequency Generator

• Allows for precise matching

to VCSO

• Controllable down to 10Hz

• 2 inputs (Generator and VCSO)
• Output fed to operational amplifier for hardware

filtering of noise and amplification for display

Matched frequencies result in DC voltage

Phase Frequency Detector

• Product of previous work, controlled by 24 V source

with intensity controlled by duration of pulse (typically 1.5ms)

• Foam Coating provides mechanical damping to

reduce aftershock effects such as ringing

• Connected to DAQ which allows

MATLAB program to shock during data collection period

Shock Tower

• ADXL001-500Z
• Mounted to VCSO directly, responds synchronously

with VCSO to feedback attenuated voltage.

• Output of Accelerometer was measured at 2.43V,

changes with sensitivity of +3.3mV/G

• Fall semester we looked at raw data
• Spring semester involved filtering

and attenuation for compensation

Accelerometer

Data Acquisition Card

Test Setup

Shock Accelerometer VCSO Filter Filter Signal Generator Phase Frequency Detector DAQ PC

• The Control pin bias

voltage ranges from 0-5 volts.

• Linearity of the frequency

response was seen between 0-2 volts.

• Changes in frequency in

linear region was 1.6kHz under standard operating region of 1.0-1.1V .

Frequency Response VSCO

• Maximum Output of the

VSCO is approximately 10-12 dbm.

• Maximum input of phase

frequency detector is 13 dbm.

• Attenuator was inserted in line

with VSCO to reduce input voltage and eliminate noise.

• Improve data acquisition and

protect the integrity of the component.

Problem solved with PFD

• 3 finger tapping on

VCSO appears to knock

• utput signal out of phase
• Response remains at that

phase until the other shock before it goes even further out of phase.

• Total phase shift

represent the sum of the three individual shocks

Shocking VCSO by tapping

• Shocking by

solenoid did not produce consistent data as finger tapping after repeat trials

• Results were

inconsistent because more vibrations occur in SAW and possibly electromagnetic effect.

Shocking by Solenoid

• Accelerometer
• utput was too high

which exceeds input voltage on VSCO of 5V.

• Output of

accelerometer produced

• versensitive signals

Problem with Accelerometer

Filtering:

• Software lowpass butterworth filter

Pre-Spring Break Results

Tap Testing:

• EM interference
• Code revised for manual tapping
• Insignificant disturbances

Pre-Spring Break Results

Differential Op-Amp

• Low-noise
• DAQ inputs changed to single-ended
• Hardware + software filtering
• Wider voltage range
• O-scope test point

Pre-Spring Break Results

Post Spring Break

Vibration Reduction

• Oscillators secured with nylon straps
• VCSO’s shimmed internally
• Wires taped and organized

New Accelerometers

• Faulty accelerometer:
• ADXL001-500
• Only accelerometer in possession before spring break
• Output magnitude 5x too large
• Saturation at accelerations < 100g
• Confirmed with calibrated accelerometer
• New accelerometers:
• Also ADXL001-500
• Single axis
• 500g
• 22kHz bandwidth
• Able to measure the acceleration levels

necessary

Acceleration Sensitivity

• New accelerometers to move forward
• Most important task to achieving compensation
• Data processing and noise filtering have paid off
• Test each axis and superimpose compensations
• Accelerometer Output Attenuation Equation:
• Γ = Acceleration Sensitivity (1/g)
• Fo = Oscillator Frequency (Hz)
• m = Frequency Control Curve Slope (Hz/V)
• S = Accelerometer Sensitivity (V/g)

Compensation Circuit

• Potentiometers for fine tuning attenuation level
• Accommodates 3 axes
• Operates around 1V (most linear region on the VCSO control input)
• Switches to toggle compensation
• Overall gain determined by VCSO acceleration sensitivity

Accelerometer Voltage Divider Non-inverting Summing Amplifier VCSO

Compensation Circuit

Ghosting

• Inherent with all scanning data

acquisition units

• Capacitor voltage does not have

time to change to the proper level

• Causing data corruption
• Attempted Remedies
• Decrease sample rate
• Increase Input Switching

Time

• Still an issue as will be shown

Ghosting

Compensation On, Sample Rate = 200kHz

Ghosting

Compensation On, Sample Rate = 500kHz

X-Axis Testing

X Y Z

X-Axis Testing

Compensation Off

X-Axis Testing

• Actual attenuation ratio not corresponding to calculations yet
• Investigate possible ghosting in x-axis compensated result

Compensation On

X-Axis Testing

Y-Axis Testing

X Y Z

Y-Axis Testing

Ghosting Effect

Y-Axis Testing

• No compensation necessary

Accelerometer Input Grounded (Ghosting Removed)

Y-Axis Testing

Timeline

Budget

Total Cost: $430 Given Materials:

• National Instruments X series USB-6353 Data Acquisition Card
• NI-DAQmx software
• MATLAB 2009
• Giga-tronics 6060B Signal Generator
• Phonon 400MHz VCSOs
• B&K 9130 triple output power supply
• Phase Frequency Detectors
• 2x Shock Tower
• Passive Circuit Components

Materials to Purchase:

• Accelerometers

$250

• TLC2262CP op-amps

$5

• Nylon Straps

$25

• Phase Frequency Detectors

$150